- Downloading VLC player, thought original DVD player may be corrupted.
- Not the DVD disk itself, cause its playing fine DVD player.
- Playing MP3 files on computer is fine, which suggested computer's audio driver installed correctly
- Playing Youtube video on the internet fine, which suggested computer's memory & performance maybe acceptable.
- No evidence suggested possible virus attacking.
- Failed power components for not enough power juice, or bad DVD unit itself.
Answer: It was configured as a second DVD Player daisy-chained to another old CD-rom to PIDE channel. Due to certain compatibility issue, DVD was suffered with slow performance, once it was isolated from old CD-rom, DVD playing is normal.